The invention relates to an electrical system for vehicles for vehicles having a combustion engine, a generator, a starter motor that can be manually activated, a starter battery and a breaker, controlled by a crash sensor and arranged in a starter circuit which includes the starter battery and the starter motor.
Electrical systems for vehicles are designed to prevent overheating and overload of wires caused by electrical short circuits in the event of a crash. For this purpose, most circuits are protected from short circuits by use of fuses and/or circuit breakers, except for the starter cable, i.e., the connection between the positive pole of the battery and the starter motor. Because of the high current of the starter motor, there is no suitable fuse for this cable.
EP 0 825 068, discloses a starter circuit which includes a breaker that interrupts the flow of current in response to a signal from a crash sensor, wherein the breaker immediately interrupts power to the starter cable in the event of a crash. The breaker may be constructed as a pyrotechnic device which triggers an explosion that interrupts the main path of the current. DE 196 06 448 and DE 44 02 994 respectively show a breaker of this type in the form of a battery terminal which is ordinarily actuated with the assistance of a pyrotechnical blasting cap in cooperation with an air bag sensor. For this purpose, the breaker is provided with two contact pieces whose contacting surfaces normally lie on top of each other and which may be separated from each other by pyrotechnical means, more specifically in the form of a propellant charge, when the vehicle undergoes an abnormally high acceleration. According to DE 44 25 307, the propellant charge may constitute a structural part of a battery terminal.
All of the prior approaches result in a permanent interruption of the starter circuit when a crash occurs. As a result, the vehicle cannot be started after the crash sensor has been triggered. This is particularly disadvantageous when the air bag sensor is triggered on account of a failure, or in a minor accident, when the driver would like to at least drive the car to the garage. In such a case, the vehicle can no longer be moved without repair.
An electrical system for vehicles is described in DE 40 28 242 wherein there is provided a second battery for supplying electrical accessories, in addition to a starter battery. The two batteries are connected together when the voltage of the electrical system battery is higher than the voltage of the starter battery. Conversely, when the voltage of the electrical system battery has dropped relative to the voltage of the starter battery, the two batteries are separated from each other. Accordingly, the generator is capable of recharging both batteries. In this solution, the second electrical accessory battery and the starter battery are permanently connected in parallel and the starter battery alone may be disconnected by a starter battery breaker in the starter circuit.
A diagram of connections for achieving an appropriate function in connection with the above mentioned reference is described in DE 38 41 769. WO 96133078 describes a battery terminal cooperating with a switch in the line leading to the battery, the switch being provided with monitoring means for controlling the switch in accordance with the signals received at its monitoring inputs.
It is the object of the present invention to make it possible to restart vehicles having a starter circuit breaker after response of the crash sensor and the irreversible interruption of the starter circuit in response thereto.
According to the invention, there is provided a bypass electrical switch which may be actuated by a control circuit, that is used in to detect whether there is a short circuit in the starter circuit, such that, after interruption of the starter circuit on account of a activation of a breaker, an electrical connection may be re-established between the starter and a battery in the starter circuit by the bypass switch, when the starter circuit is free from any short circuit.
A feature of the preferred embodiment of the invention is that a bypass-switch is arranged to re-connect the starter circuit when the control circuit senses that the starter circuit is free from any short circuit. Thus, the engine may be re-started when the mechanical damage occasioned by the crash is not so severe as to destroy the functionality of the starter. The energy source which is connected by the bypass switch to the starter circuit may be any available battery within the electrical system. The solution according to the invention is independent of the position of the breaker, which may also, e.g. be located in the ground cable of the starter battery.
According to a preferred embodiment of the invention, the bypass switch is preferably arranged parallel to the breaker, to thereby restore an electrical connection between the starter and the starter battery. The starter battery is therefore used for restarting the vehicle after the crash (as far as it has not been destroyed). The safety relevant function of the breaker is preserved in that the response of the breaker to the crash sensor prevents overload of the wires in the event of an accident, and on the other hand, the vehicle can be restarted when it is in running order. The electronics of the control circuit senses whether there is any short circuit in the starter wire and triggers the connection means when there is none.
In an alternative embodiment of the invention for electrical systems having a second battery, the bypass switch makes an electrical connection between the starter circuit and the second battery of the electrical system in the event the response of the breaker permanently interrupts the starter circuit. The energy source use for the starter thereby is the second battery of the electrical system, which ordinarily is not damaged in a frontal collision, as it may be located in the rear part of the vehicle. In this arrangement, the commutator that is already provided in such vehicles can function as the bypass switch when it is provided with a suitable control circuit for sensing short circuits in the starter circuit.
The invention will be more fully explained hereinafter with reference to two exemplary embodiments that are illustrated in the Figures.